28 THE EVOLUTION OF PLANTS 



The last-mentioned is too little known to be 

 really comparable to the others. 



We are, here, only interested in the first three 

 of these Floras. Our object will be, so far as the 

 fragmentary evidence permits, to trace back 

 the main lines of descent of the higher classes 

 of plants, to Palaeozoic times. 



CHAPTER II 



THE EVOLUTION OF THE FLOWERING 

 PLANTS THE PROBLEM 



TEN years ago, Professor Vines, in his ad- 

 dress to the Botanical Section of the British 

 Association, was at the pains to take a census 

 of the Vegetable Kingdom, according to the 

 best statistics available at the time. A census 

 of that kind is of course very different from the 

 census we are expecting this year; it is a count 

 of species, not of individuals. Botanists differ 

 very much as to the limits of species; for ex- 

 ample, in Hooker's Students' Flora only four 

 British species of Rubus (the Blackberry and 

 Raspberry genus) are recognised, while in Druce's 

 List of British Plants 133 species are given! 

 However, that is happily an extreme case, and 

 as the object of a plant-census is to get at pro- 

 portional rather than absolute numbers, the 



